xhci: Remove BUG in xhci_setup_addressable_virt_dev

We may have more speed types in the future, so fail gracefully, rather
than causing the kernel to panic.

BUG() was called if the device speed was unknown when setting max packet
size.  Set the max packet size at the same time as the slot speed and
get rid of one switch statement with BUG() option completely.

[Note: Sarah merged a patch that she wrote that touched the
xhci_setup_addressable_virt_dev function with this patch from Mathias
for clarity.]
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/xhci-mem.c

@@ -1055,6 +1055,7 @@ int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *ud
 	struct xhci_ep_ctx	*ep0_ctx;
 	struct xhci_slot_ctx    *slot_ctx;
 	u32			port_num;
+	u32			max_packets;
 	struct usb_device *top_dev;
 
 	dev = xhci->devs[udev->slot_id];
@@ -1072,15 +1073,20 @@ int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *ud
 	switch (udev->speed) {
 	case USB_SPEED_SUPER:
 		slot_ctx->dev_info |= cpu_to_le32(SLOT_SPEED_SS);
+		max_packets = MAX_PACKET(512);
 		break;
 	case USB_SPEED_HIGH:
 		slot_ctx->dev_info |= cpu_to_le32(SLOT_SPEED_HS);
+		max_packets = MAX_PACKET(64);
 		break;
+	/* USB core guesses at a 64-byte max packet first for FS devices */
 	case USB_SPEED_FULL:
 		slot_ctx->dev_info |= cpu_to_le32(SLOT_SPEED_FS);
+		max_packets = MAX_PACKET(64);
 		break;
 	case USB_SPEED_LOW:
 		slot_ctx->dev_info |= cpu_to_le32(SLOT_SPEED_LS);
+		max_packets = MAX_PACKET(8);
 		break;
 	case USB_SPEED_WIRELESS:
 		xhci_dbg(xhci, "FIXME xHCI doesn't support wireless speeds\n");
@@ -1088,7 +1094,7 @@ int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *ud
 		break;
 	default:
 		/* Speed was set earlier, this shouldn't happen. */
-		BUG();
+		return -EINVAL;
 	}
 	/* Find the root hub port this device is under */
 	port_num = xhci_find_real_port_number(xhci, udev);
@@ -1147,31 +1153,10 @@ int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *ud
 	/* Step 4 - ring already allocated */
 	/* Step 5 */
 	ep0_ctx->ep_info2 = cpu_to_le32(EP_TYPE(CTRL_EP));
-	/*
-	 * XXX: Not sure about wireless USB devices.
-	 */
-	switch (udev->speed) {
-	case USB_SPEED_SUPER:
-		ep0_ctx->ep_info2 |= cpu_to_le32(MAX_PACKET(512));
-		break;
-	case USB_SPEED_HIGH:
-	/* USB core guesses at a 64-byte max packet first for FS devices */
-	case USB_SPEED_FULL:
-		ep0_ctx->ep_info2 |= cpu_to_le32(MAX_PACKET(64));
-		break;
-	case USB_SPEED_LOW:
-		ep0_ctx->ep_info2 |= cpu_to_le32(MAX_PACKET(8));
-		break;
-	case USB_SPEED_WIRELESS:
-		xhci_dbg(xhci, "FIXME xHCI doesn't support wireless speeds\n");
-		return -EINVAL;
-		break;
-	default:
-		/* New speed? */
-		BUG();
-	}
+
 	/* EP 0 can handle "burst" sizes of 1, so Max Burst Size field is 0 */
-	ep0_ctx->ep_info2 |= cpu_to_le32(MAX_BURST(0) | ERROR_COUNT(3));
+	ep0_ctx->ep_info2 |= cpu_to_le32(MAX_BURST(0) | ERROR_COUNT(3) |
+					 max_packets);
 
 	ep0_ctx->deq = cpu_to_le64(dev->eps[0].ring->first_seg->dma |
 				   dev->eps[0].ring->cycle_state);